This invention is directed to naphtha, kerosene or diesel hydrocracking processes employing large pore zeolite catalysts such as Zeolite Beta or Ultra Stable Y (USY), which are loaded with noble metals such as Pt or Pd or with transition metal such as Ni in combination with Mo or W. Preferably, low hydrogen partial pressures and feedstocks relatively rich in hydrogen and low in aromatics are employed, in order to extend catalyst cycle length.
Many refineries have been required to reduce the T90 (temperature at which 90% of the gasoline pool boils as measured by an atmospheric distillation such as ASTM D-86) of the gasoline pool in order to meet more stringent governmental regulations being enacted in some areas. This requires removal of heavy feeds, such as FCC gasoline, from the gasoline pool. Such heavy feeds then enter the kerosene market, potentially forcing the price of kerosene to drop. It is therefore desirable to find new uses for FCC gasoline and kerosene, boiling in the range from 300xc2x0 to 400xc2x0 F. The process of the instant invention will enable refineries to convert these feeds to gasolines which meet the criteria of governmental entities such as the EPA and CARB.
Catalysts comprising large pore zeolites loaded with metals combinations such as Nixe2x80x94Mo or Nixe2x80x94W have been previously employed in hydrocracking applications. U.S. Pat. No. 5,401,704 (Absil et al., hereafter Absil) discloses a hydrocracking process employing a catalyst comprising small crystal zeolite Y. Preferred feeds possess at least 70 wt. % hydrocarbons having a boiling point of at least 400xc2x0 F. Lighter feeds are desired in the instant invention. Zeolite Y may be loaded with a metal or combinations of metals for hydrogenation purposes, such as Pt, Pd, Nixe2x80x94W or Coxe2x80x94Mo. Absil does not, however, teach the concept of extinction recycle hydrocracking at hydrogen partial pressures below 400 psig, as does the instant invention.
U.S. Pat. No. 5,500,109 (Keville et al., hereafter Keville #1) discloses a hydrocracking catalyst which comprises a large pore zeolite (such as USY) loaded with metals combinations such as NiW. This catalyst is extruded with an alumina binder. The disclosure suggests, however, that feeds intended for use with this catalyst are gas oils and residua, rather than the lighter feeds of the instant invention. There is also no mention of extinction recycle hydrocracking.
U.S. Pat. No. 5,378,671 (Keville et al., hereafter Keville #2) is also directed to hydrocracking of gas oils and residua with catalysts comprising large pore zeolites.
U.S. Pat. No. 4,968,402 discloses a process for producing high octane gasoline from heavy feedstocks containing over 50 wt. % aromatics such as polynuclear aromatics. A catalyst comprising MCM-22 is employed, preferably loaded with NiW.
U.S. Pat. No. 4,851,109 discloses a two-stage process for hydrocracking feeds such as coker gas oils, vacuum gas oils, as well as light and heavy cycle oils. In the first stage, the feed is hydrocracked with a catalyst comprising a large pore zeolite, such as zeolite Y or USY. The catalyst may be loaded with a hydrogenation component such as a NiW combination. In the second stage, hydroprocessing occurs over a catalyst comprising zeolite beta.
U.S. Pat. No. 3,923,641 to Morrison and U.S. Pat. No. 4,812,223 to Hickey, Jr. et al. teach the conversion of C5+ and C6+ naphthas over noble metal-containing zeolite Beta catalyst, preferably a steamed zeolite Beta catalyst. There is no mention of extinction recycle hydrocracking.
U.S. Pat. No. 4,968,403 to Kirker et al is primarily directed to upgrading hydrocarbons employing a catalyst comprising MCM-22, which is loaded with base metals. There is only a general teaching of recycling bottoms to the hydrocracker. Feeds having an aromatic content of over 75 wt. % are suitable for use in Kirker, whereas in the instant invention, aromatics content is to be no greater than 40 wt. % if the catalyst is loaded with base metals. Kirker teaches away from the use of USY, whereas USY is the preferred zeolite in the instant invention.